CODEWITHSUNDEEP
haskellrecord
mikejay
mikejay

Reputation: 17

adding elements of a record type

So I have a record type:

data Box = Box { edge :: Char
                   , time1 :: [Int]
                   , time2 :: Int
                   }
             deriving Eq

and this list over here:

list_of_boxes :: [Box]

How can I sum the values for time1 in each box of the list, then find which box gives the highest value for time1?

Upvotes: 1

Views: 170

Answers (2)

chi
chi

Reputation: 116139

This will sum every list only once:

import Data.List
import Data.Ord
snd . maximumBy (comparing fst) . map (\x -> (sum . time1 $ x , x)) $ list_of_boxes

The above can be shortened a bit using arrows:

import Control.Arrow
snd . maximumBy (comparing fst) . map (sum . time1 &&& id) $ list_of_boxes

Upvotes: 1

jamshidh
jamshidh

Reputation: 12070

This will work

maximumBy (compare `on` sum . time1) list_of_boxes

You will need to import Data.List and Data.Function.

Upvotes: 6

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